FIND YOUR STATE

1. Alaska

2. Arizona

3. California

a. Central California

b. Southern California

4. Colorado

5. Florida

6. Idaho

7. Iowa

8. Maine

9. Minnesota

10. Missouri

11. Nevada

12. New Mexico

13. New York

14. North Carolina

15. Pennsylvania

16. South Carolina

17. Texas

18. Utah

19. Virginia

1. ALASKA ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Alaska’s temperatures are By 2050, daily high The recent heat wave in warming twice as fast as temperatures in Alaska the Gulf of Alaska reduced the global average1, and may increase up to 8°F fisheries catch and led to Denali National Park is now compared to 1981-2000; an approximately 80% 3.3°F warmer than it was the coldest nights may reduction in the allowable 100 years ago.2 increase by more than Pacific Cod quota in 2018.6 12°F, and the number of HEAT Average temperatures nights below freezing may Permafrost thawing is during winter in Alaska are decrease by 20+ nights per damaging buildings, roads, nearly 6°F higher than in year.4 and cultural heritage sites 1970.3 and structures as the The number of heat wave ground sinks.7 days could more than triple by 2050.5

The number of coastal The 100-year coastal Flooding and erosion of flood days observed on the floodplain in Alaska is coastal and river areas Pacific Coast in the period projected to expand from affect over 87% of the between 2005 and 2014 nearly 13,000 square miles Alaska Native was more than six times as to more than 15,000 communities.11 COASTAL high as that observed in square miles by the 1950s.8 Of the 735 midcentury, which will As the sea ice edge moves FLOODING coastal flood days since affect around 3,000 more northward, storms produce 1950, 75% are attributed to residents.10 larger waves and cause human-caused climate more coastal flooding and change.9 erosion, threatening communities.12

Alaska has more area The area burned by Wildfires and temperature burning in wildfires than wildfires from 2006-2100 increases have caused any other state, and the could be 120 million acres changes in forest and wildfire season is now 40% if greenhouse gas vegetation types, which longer than in the 1950s, emissions continue affects wildlife and rural with nearly 350,000 more unabated.14 communities.15 WILDFIRES acres burned each year, and on average around 40 Wildfire smoke exposure is more large wildfires each a concern for children and year – twice as many as 60 people with chronic years ago.13 respiratory and cardiovascular conditions.16

1 https://nca2018.globalchange.gov/chapter/26#fig-26-1 • The statewide annual average temperature record shows no clear change from 1925 to 1976 due to high variability, but from 1976–2016 a clear trend of +0.7°F per decade is evident. 2 https://www.climatecentral.org/gallery/graphics/100-years-of-warming-at-the-national-parks • Source data from Hadley CRU Hi-Res Dataset. 3 https://www.climatecentral.org/gallery/graphics/seasonal-warming-trends-across-the-us

• Trends for meteorological seasons are calculated using monthly average temperature data between 1970 and 2017 (data from the NOAA NCEI). For clarity and the ability to compare different seasons, authors omitted the annual data points and displayed only the linear trends over time. 4 https://nca2018.globalchange.gov/chapter/26/ • These temperature projections assume the high emissions scenario RCP8.5. 5 http://assets.statesatrisk.org/summaries/Alaska_report.pdf • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline (1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 6 https://nca2018.globalchange.gov/chapter/26/ • These reductions are having significant impacts on Alaska fishing communities and led the governor of Alaska to ask the Federal Government to declare a fisheries disaster. Events such as these are requiring the use of multiple, alternative models to appropriately characterize uncertainty in future population trends and fishery harvests. 7 https://nca2018.globalchange.gov/chapter/26/ • As evidenced by Nelson et al. 2001, Hong et al. 2014, and Raynolds et al. 2014. 8 https://www.climatecentral.org/gallery/graphics/natural-human-caused-coastal-flood-days-in-the-us • Authors subtracted yearly estimates for human-caused global sea level rise based on Kopp et al. 2016, from hourly water level records at 27 tide gauges around the United States. They then compared how many days the water level exceeded the local threshold for nuisance flooding — with or without the subtractions. 9 https://www.climatecentral.org/gallery/graphics/natural-human-caused-coastal-flood-days-in-the-us • Authors subtracted yearly estimates for human-caused global sea level rise based on Kopp et al. 2016, from hourly water level records at 27 tide gauges around the United States. They then compared how many days the water level exceeded the local threshold for nuisance flooding — with or without the subtractions. 10 http://assets.statesatrisk.org/summaries/Alaska_report.pdf • Coastal flooding could disproportionately affect Native Alaskans, who make up the majority of residents in Alaska’s remote coastal villages along the western and northern coasts where topography is relatively flat. 11 https://nca2018.globalchange.gov/chapter/26/ • Estimate based on the assessment of five separate studies: Cochran et al. 2013, Inter-agency Working Group 2009, U.S. Army Corps of Engineers 2009, U.S. Government Accountability Office 2009, and U.S. General Accountability Office 2003. 12 https://nca2018.globalchange.gov/chapter/26/ • As highlighted in Gibbs and Richmond 2015, the National Assessment of Shoreline Change: Historical Shoreline Change along the North Coast of Alaska. 13 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 14 https://nca2018.globalchange.gov/chapter/26/ • These projections of area burned by wildfires assume the high emissions scenario RCP8.5. 15 https://nca2018.globalchange.gov/chapter/26/ • The vegetation of forested interior Alaska now has less acreage of older spruce forest and more of post- fire early successional vegetation, birch, and aspen than it did prior to 1990. This change favors shrub- adapted wildlife species such as moose but also destroys the slow-growing lichens and associated high- quality winter range that caribou prefer, though the effects of fire-driven habitat changes to caribou population dynamics are uncertain. 16 https://nca2018.globalchange.gov/chapter/26/

• Air conditioning in homes is rare in Alaska, so relief is seldom available for at-risk persons to escape high temperatures or from smoke exposure due to wildfires, assuming proper filters are not installed. 2. ARIZONA

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Arizona is 4th-fastest Heat wave days in Arizona Tucson ranks 6th in U.S. warming state in U.S.1 are expected to more than cities with the largest triple by 2050 from 15 to 50 increase in ‘disease danger Phoenix is 2nd-fastest days a year.4 days’ (risk of disease warming city in the U.S. transmission by followed by Prescott as the ‘Dangerous’ heat days are mosquitoes), increasing by 5th and Tucson as the 7th.2 projected to grow from 50 29 days since 1970.7 HEAT days a year to 80 by 2050.5 Average temperatures in By midcentury, Arizona Arizona during spring have Number of days above summers could see 20% warmed by 4°F since 100°F in Phoenix may reduction in electricity 1970.3 nearly double from 80 to generation capacity.8 150 by end of century.6

Drought in the By 2050, the severity of Reduced water flow from southwestern U.S. is widespread summer the Colorado River is declining the western drought is projected to impacting Arizona’s water snowpack, and this along more than triple in Arizona, supply; Tucson gets almost with rising temperatures the second largest increase all their water from the have reduced water flow behind Washington.10 River, while Phoenix down the Colorado River.9 receives about half its DROUGHT supply.11

Higher number of cases of Valley fever have occurred in Arizona from drier conditions.12

Arizona now sees three By 2050, Arizona is Nearly 3 million people times more fires burning projected to see over one living in Arizona – 45% of per year than in the 1970s, more month of high wildfire the state’s population – are which has led to thousands potential, leading to 115 at- at elevated risk of wildfire.15 WILDFIRES of more acres burned each risk days each year.14 year.13 Infrastructure is especially vulnerable to increased wildfires.16

1 http://statesatrisk.org/arizona/extreme-heat • Warming rates are evaluated from year 1970 to today. 2 https://www.climatecentral.org/news/fastest-warming-cities-20535 • This analysis considered the top 200 largest metro areas in the U.S. and calculated their average annual temperature from 1981-2010. To determine which of those 200 cities have been warming the fastest, authors calculated how average annual temperatures have been changing since 1965. 3 https://www.climatecentral.org/gallery/graphics/seasonal-warming-trends-across-the-us

• Trends for meteorological seasons are calculated using monthly average temperature data between 1970 and 2017 (data from the NOAA NCEI). For clarity and the ability to compare different seasons, authors omitted the annual data points and displayed only the linear trends over time. 4 http://statesatrisk.org/arizona/extreme-heat • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline (1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 5 http://statesatrisk.org/arizona/extreme-heat • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 6 https://nca2018.globalchange.gov/chapter/1#fig-1-16 • These temperature projections assume the high emissions scenario RCP8.5. 7 https://www.climatecentral.org/news/us-faces-a-rise-in-mosquito-disease-danger-days-21903 • Temperature trends were calculated using average daily temperature data from the Applied Climate Information System (rcc-acis.org). Years with more than 30 days of missing data were excluded from the analysis. The temperature range of disease transmission (61-93F) as well as the range for peak transmission (79-84F) were chosen based on the findings in Mordecai et al. 2017. 8 https://nca2018.globalchange.gov/chapter/25#fig-25-8 • Heat-induced reduction of energy efficiency calculated based on a higher emissions scenario (SRES A2). 9 https://nca2018.globalchange.gov/chapter/14/ • Highlighted by McCabe et al. 2017, Udall and Overpeck 2017, and Woodhouse et al. 2016. 10 http://statesatrisk.org/arizona/drought • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 11 http://statesatrisk.org/arizona/drought • If upstream states continue to be unable to make up the shortage, Lake Mead, whose surface is now about 1,085 feet above sea level, will drop to 1,000 feet by 2020. Under present conditions, that would cut off much of Arizona’s water supply. 12 https://nca2018.globalchange.gov/chapter/14/ • Valley fever can cause persistent flu-like symptoms, with over 40% of cases hospitalized and 75% of patients unable to perform their normal daily activities for weeks, months, or longer. Relationship between valley fever cases and drier conditions established by Coopersmith et al. 2017. 13 http://www.climatecentral.org/gallery/graphics/hotter-years-more-fires • Authors analyzed 45 years of U.S. Forest Service records of large wildfires (those fires burning more than 1,000 acres) from the western U.S. in the new report, “Western Wildfires: A Fiery Future.” 14 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 15 http://statesatrisk.org/arizona/wildfires • Individuals living within the wildland-urban interface, where developed wild lands converge and intersperse, are at elevated risk for wildfire. 16 http://statesatrisk.org/arizona/wildfires

3. CALIFORNIA

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES California has warmed Heat wave days in San Francisco mosquito 2.5°F on average since California are projected to season is now 2 weeks 1970,1 and Yosemite more than triple by 2050, longer than during the National Park has warmed from 15 to more than 45 1980s.5 4.5°F over the past days per year.4 HEAT century.2 Riverside is the Heat waves in CA have 4th fastest warming city in already caused hundreds the U.S.3 of deaths, thousands of hospital visits, and billions in economic costs.6

Higher temperatures The severity of widespread The increase in heat and intensified the 2011-2016 summer drought in reduction of snow have drought, and led to the California is projected to amplified recent water largest ‘snow drought’ on almost triple by the end of shortages.9 record as more the century.8 DROUGHT precipitation fell as rain.7 The recent drought led to 10,000+ lost jobs and $900M of gross crop revenue lost.10

The number of fires and The frequency of wildfires 11+ million people in amount of acres burning may increase by 25% in California (30% of the state annually in California has the Southwest by end of population) are at elevated roughly doubled since the century, along with a risk of wildfires.14 1970s.11 In 2018, 400,000+ tripling of very large fires.13 WILDFIRES acres burnt – nearly 3 Wildfires in California in times the amount in the 2017 and 2018 resulted in 1970s.12 over $42 billion in damages.15

Sea level has risen around Projected sea level rise by 200,000+ more people are 9 inches at Golden Gate 2050 could make 100-year projected to be at risk of Bridge and in San Diego floods in La Jolla, Los coastal flooding by 2050.20 over past century.16 Angeles, and San Diego COASTAL Scientists say 150+ coastal 100 times more likely.18 Sea level rise and storm FLOODING flood days in San Fran and surge may erode 2/3 of La Jolla over past decade Areas in coastal floodplain southern California are 80%+ human-caused.17 zone could double by beaches by 2100.21 2050.19

1 https://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 https://www.climatecentral.org/gallery/graphics/100-years-of-warming-at-the-national-parks • Source data from Hadley CRU Hi-Res Dataset. 3 https://www.climatecentral.org/news/fastest-warming-cities-20535

• This analysis considered the top 200 largest metro areas in the U.S. and calculated their average annual temperature from 1981-2010. To determine which of those 200 cities have been warming the fastest, authors calculated how average annual temperatures have been changing since 1965. 4 http://assets.statesatrisk.org/summaries/California_report.pdf • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline (1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 5 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553#dropdown • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 6 https://nca2018.globalchange.gov/chapter/25/ • Compared to non-heat wave summer days, it is estimated that the event led to an additional 600 deaths, 16,000 emergency room visits, 1,100 hospitalizations in California, and economic costs of $5.4 billion (in 2008 dollars). 7 https://nca2018.globalchange.gov/chapter/25/ • Impact of higher temperatures on the 2011-2016 drought outlined by Williams et al. 2015, Diffenbaugh et al. 2015, Griffin and Annchukaitis 2014, Luo et al. 2017, and Shukla et al. 2015; impact on low snowpack outlined by Mote et al. 2016, Berg and Hall 2017, Luo et al. 2017, and Belmecheri et al. 2016. 8 http://assets.statesatrisk.org/summaries/California_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 9 https://nca2018.globalchange.gov/chapter/25/ • Evidenced by Williams et al. 2015, Berg and Hall 2017, Diffenbaugh et al. 2015, Mao et al. 2015, and Seager et al. 2015. Snow droughts can arise from a lack of precipitation, temperatures that are too warm for snow, or a combination of the two. 10 https://nca2018.globalchange.gov/chapter/25/ • The California drought led to losses of more than 10,000 jobs and the fallowing of 540,000 acres (220,000 hectares), at a cost of $900 million in gross crop revenue in 2015. 11 https://www.climatecentral.org/gallery/graphics/hotter-years-more-fires • Authors analyzed 45 years of U.S. Forest Service records of large wildfires (those fires burning more than 1,000 acres) from the western U.S. in the new report, “Western Wildfires: A Fiery Future.” 12 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 13 https://nca2018.globalchange.gov/chapter/25/ • The increased projected fire frequency is based upon a higher emissions scenario (SRES A2). 14 http://assets.statesatrisk.org/summaries/California_report.pdf • Individuals living within the wildland-urban interface, where developed wild lands converge and intersperse, are at elevated risk for wildfire. 15 https://www.ncdc.noaa.gov/billions/events/US/1980-2018 • This is a sum of the costs of Weather and Climate Billion-Dollar Disasters (NOAA data) stemming from California wildfires in 2017 and 2018. 16 https://nca2018.globalchange.gov/chapter/25/ • The increased projected fire frequency is based upon a higher emissions scenario (SRES A2). 17 https://www.climatecentral.org/news/climate-change-increases-sunny-day-floods-20784#dropdown

• This analysis is based on a broader February 2016 Climate Central analysis that looked at the human- caused sea level rise contribution to nuisance flooding over a 65-year period. That study focused on 27 tidal gauges with high quality hourly water level records dating back several decades. 18 https://www.climatecentral.org/gallery/graphics/sea-level-rise-is-increasing-coastal-flood-risk • Source data comes from the Intermediate High NCA Projection and Climate Central. 19 http://assets.statesatrisk.org/summaries/California_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 20 http://assets.statesatrisk.org/summaries/California_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 21 https://nca2018.globalchange.gov/chapter/25/ • Estimated by Vitousek et al. 2017.

3a. CALIFORNIA – CENTRAL

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES The hottest year on record Days above 100°F in Santa Maria and Fresno, in Bakersfield, Monterey, Fresno may triple by end of CA rank 3rd and 9th for U.S. and Santa Maria, CA century if current emissions cities with the largest occurred during the trends continue, from 30 increase in ‘disease danger 2010s.1 days’ (risk of disease HEAT days currently to 97 days by 2100.2 transmission by mosquitos) increasing by 39 and 27 days since 1970, respectively.3

Higher temperatures The severity of widespread The increase in heat and intensified the 2011-2016 summer drought in reduction of snow have drought, and led to the California is projected to amplified recent water largest ‘snow drought’ on almost triple by the end of shortages.6 record as more the century.5 DROUGHT precipitation fell as rain.4 The recent drought led to 10,000+ lost jobs and $900M of gross crop revenue lost.7

The number of fires and The frequency of wildfires Wildfires in California in amount of acres burning may increase by 25% in 2017 and 2018 resulted in annually in California has the Southwest by end of over $42 billion in roughly doubled since the century, along with a damages.11 WILDFIRES 1970s.8 In 2018, 400,000+ tripling of very large fires.10 acres burnt – nearly 3 times the amount in the 1970s.9

1 https://www.climatecentral.org/gallery/graphics/hottest-years-for-us-cities • Data was gathered from the Applied Climate Information System. Average annual temperature was determined using the average of days (not the average of months). Years with more the 30 days of missing data were removed from the analysis. In case of a tie (22 occurrences), the most recent year is represented. Former Weather Channel meteorologist Guy Walton maintains a comprehensive records database, analyzing monthly, annual, and decadal records trends. 2 https://www.climatecentral.org/gallery/graphics/future-days-above-95f • Projections of the days each year above a threshold temperature are based on a downscaled and bias- corrected ensemble of climate models known as CMIP5 (the same models used in the IPCC). Each labeled year shows the average of the preceding 20 years. Data for 2016 are the annual averages of a gridded historical data set (Daymet, Oak Ridge National Lab) for 1997-2016. 3 https://www.climatecentral.org/news/us-faces-a-rise-in-mosquito-disease-danger-days-21903 • Temperature trends were calculated using average daily temperature data from the Applied Climate Information System (rcc-acis.org). Years with more than 30 days of missing data were excluded from the analysis. The temperature range of disease transmission (61-93F) as well as the range for peak transmission (79-84F) were chosen based on the findings in Mordecai et al. 2017. 4 https://nca2018.globalchange.gov/chapter/25/

• Impact of higher temperatures on the 2011-2016 drought outlined by Williams et al. 2015, Diffenbaugh et al. 2015, Griffin and Annchukaitis 2014, Luo et al. 2017, and Shukla et al. 2015; impact on low snowpack outlined by Mote et al. 2016, Berg and Hall 2017, Luo et al. 2017, and Belmecheri et al. 2016. 5 http://assets.statesatrisk.org/summaries/California_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 6 https://nca2018.globalchange.gov/chapter/25/ • Evidenced by Williams et al. 2015, Berg and Hall 2017, Diffenbaugh et al. 2015, Mao et al. 2015, and Seager et al. 2015. Snow droughts can arise from a lack of precipitation, temperatures that are too warm for snow, or a combination of the two. 7 https://nca2018.globalchange.gov/chapter/25/ • The California drought led to losses of more than 10,000 jobs and the fallowing of 540,000 acres (220,000 hectares), at a cost of $900 million in gross crop revenue in 2015. 8 https://www.climatecentral.org/gallery/graphics/hotter-years-more-fires • Authors analyzed 45 years of U.S. Forest Service records of large wildfires (those fires burning more than 1,000 acres) from the western U.S. in the new report, “Western Wildfires: A Fiery Future.” 9 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 10 https://nca2018.globalchange.gov/chapter/25/ • The increased projected fire frequency is based upon a higher emissions scenario (SRES A2). 11 https://www.ncdc.noaa.gov/billions/events/US/1980-2018 • This is a sum of the costs of Weather and Climate Billion-Dollar Disasters (NOAA data) stemming from California wildfires in 2017 and 2018. 3b. CALIFORNIA – SOUTHERN

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Riverside is the 4th fastest The number of dangerous Heat waves in California warming city in the U.S.1 heat days observed each have already caused year are projected to hundreds of deaths, The hottest year on record almost double in Los thousands of hospital visits, HEAT in San Diego and Palm Angeles by 2050.3 and billions in economic Springs occurred during costs.4 the 2010s.2

Higher temperatures The severity of widespread The increase in heat and intensified the 2011-2016 summer drought in reduction of snow have drought, and led to the California is projected to amplified recent water largest ‘snow drought’ on almost triple by the end of shortages.7 record as more the century.6 DROUGHT precipitation fell as rain.5 The recent drought led to 10,000+ lost jobs and $900M of gross crop revenue lost.8

The number of fires and Without action to curb Wildfires in California in amount of acres burning climate change, there could 2017 and 2018 resulted in annually in California has be a 25% increase in the over $42 billion in roughly doubled since the frequency of wildfires in the damages.12 WILDFIRES 1970s.9 In 2018, 400,000+ Southwest by end of acres burnt – nearly 3 century, along with a times the amount in the tripling of very large fires.11 1970s.10

Sea level has risen around Projected sea level rise by Sea level rise and storm 9 inches in San Diego over 2050 could make 100-year surge may erode two thirds past century.13 Scientists floods in La Jolla, Los of southern California 17 COASTAL say 150+ coastal flood Angeles, and San Diego beaches by 2100. days in La Jolla over the 100 times more likely,15 FLOODING past decade are 90% and coastal floods are human-caused.14 expected to triple in these cities by 2050.16

1 https://www.climatecentral.org/news/fastest-warming-cities-20535 • This analysis considered the top 200 largest metro areas in the U.S. and calculated their average annual temperature from 1981-2010. To determine which of those 200 cities have been warming the fastest, authors calculated how average annual temperatures have been changing since 1965. 2 https://www.climatecentral.org/gallery/graphics/hottest-years-for-us-cities • Data was gathered from the Applied Climate Information System. Average annual temperature was determined using the average of days (not the average of months). Years with more the 30 days of missing data were removed from the analysis. In case of a tie (22 occurrences), the most recent year is represented. Former Weather Channel meteorologist Guy Walton maintains a comprehensive records database, analyzing monthly, annual, and decadal records trends.

3 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 4 https://nca2018.globalchange.gov/chapter/25/ • Compared to non-heat wave summer days, it is estimated that the event led to an additional 600 deaths, 16,000 emergency room visits, 1,100 hospitalizations in California, and economic costs of $5.4 billion (in 2008 dollars). 5 https://nca2018.globalchange.gov/chapter/25/ • Impact of higher temperatures on the 2011-2016 drought outlined by Williams et al. 2015, Diffenbaugh et al. 2015, Griffin and Annchukaitis 2014, Luo et al. 2017, and Shukla et al. 2015; impact on low snowpack outlined by Mote et al. 2016, Berg and Hall 2017, Luo et al. 2017, and Belmecheri et al. 2016. 6 http://assets.statesatrisk.org/summaries/California_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 7 https://nca2018.globalchange.gov/chapter/25/ • Evidenced by Williams et al. 2015, Berg and Hall 2017, Diffenbaugh et al. 2015, Mao et al. 2015, and Seager et al. 2015. Snow droughts can arise from a lack of precipitation, temperatures that are too warm for snow, or a combination of the two. 8 https://nca2018.globalchange.gov/chapter/25/ • The California drought led to losses of more than 10,000 jobs and the fallowing of 540,000 acres (220,000 hectares), at a cost of $900 million in gross crop revenue in 2015. 9 https://www.climatecentral.org/gallery/graphics/hotter-years-more-fires • Authors analyzed 45 years of U.S. Forest Service records of large wildfires (those fires burning more than 1,000 acres) from the western U.S. in the new report, “Western Wildfires: A Fiery Future.” 10 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 11 https://nca2018.globalchange.gov/chapter/25/ • The increased projected fire frequency is based upon a higher emissions scenario (SRES A2). 12 https://www.ncdc.noaa.gov/billions/events/US/1980-2018 • This is a sum of the costs of Weather and Climate Billion-Dollar Disasters (NOAA data) stemming from California wildfires in 2017 and 2018. 13 https://nca2018.globalchange.gov/chapter/25/ • Estimated by NOAA in 2017 (“Mean sea level trend: San Diego, California”). 14 https://www.climatecentral.org/news/climate-change-increases-sunny-day-floods-20784#dropdown • This analysis is based on a broader February 2016 Climate Central analysis that looked at the human- caused sea level rise contribution to nuisance flooding over a 65-year period. That study focused on 27 tidal gauges with high quality hourly water level records dating back several decades. 15 https://www.climatecentral.org/gallery/graphics/sea-level-rise-is-increasing-coastal-flood-risk • Source data comes from the Intermediate High NCA Projection and Climate Central. 16 https://www.climatecentral.org/gallery/graphics/climate-change-increasing-frequency-of-coastal-flooding • Observed water levels were used to count present and past floods, which were driven by tides along with storm surges. Future hourly water levels are based on detailed tidal projections and sea level rise projections. 17 https://nca2018.globalchange.gov/chapter/25/ • Estimated by Vitousek et al. 2017. 4. COLORADO

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Colorado has warmed By midcentury, Colorado is The length of mosquito 2.6°F since the 1970s1 and projected to experience five season has more than over 3.5°F during the fall.2 times as many heatwaves tripled in Grand Junction, Fort Collins is 9th-fastest each year,5 and the CO since the 1980s.7 warming city in the U.S.3 number of dangerous heat days is projected to By midcentury, several HEAT The number of days above increase by 50%.6 cities in Colorado could see 95°F each summer has up to a 30% reduction in approximately doubled in electricity generation Denver since the 1970s.4 capacity during summers and are at risk of electricity shortages.8

Increasing heat and By 2050, widespread Declining snowpacks and decreasing snow have summer drought severity in runoff, along with a shift of exacerbated recent Colorado is projected to be spring runoff to earlier in droughts in the Colorado among the worst in the the season, may reduce River Basin.9 country, tripling its severity hydroelectric power compared to today.11 potential by up to 15% by DROUGHT High temperatures are 2050.12 responsible for up to half of the record-setting Colorado During a low snow season, River streamflow Colorado can observe a reductions between 2000 loss of over $150 million in and 2014.10 ski resort revenue.13

The number of fires By end of the century in the Wildfires have previously burning annually in Southwest U.S., fire degraded drinking water in Colorado has more than frequency could increase Fort Collins with sediment quadrupled since the by 25% and the frequency and cancer precursors, 1970s.14 An average year of large fires could triple requiring a multi-month WILDFIRES in the 2010s experienced without efforts to curb switch to alternative water 30 times more acres greenhouse gas supplies.17 burned by large wildfires emissions.16 than in the 1970s.15

1 http://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the National Climatic Data Center’s Climate at a Glance database. 2 https://www.climatecentral.org/gallery/graphics/seasonal-warming-trends-across-the-us • Trends for meteorological seasons are calculated using monthly average temperature data between 1970 and 2017 (data from the NOAA NCEI). For clarity and the ability to compare different seasons, authors omitted the annual data points and displayed only the linear trends over time. 3 http://www.climatecentral.org/news/fastest-warming-cities-20535

• This analysis considered the top 200 largest metro areas in the U.S. and calculated their average annual temperature from 1981-2010. To determine which of those 200 cities have been warming the fastest, authors calculated how average annual temperatures have been changing since 1965. 4 http://reportcard.statesatrisk.org/report-card/colorado/extreme_heat_grade • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 5 http://reportcard.statesatrisk.org/report-card/colorado/extreme_heat_grade • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 6 http://reportcard.statesatrisk.org/report-card/colorado/extreme_heat_grade • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 7 http://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553#dropdown • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 8 https://nca2018.globalchange.gov/chapter/25/ • Under a higher emissions scenario (SRES A2), heat-induced reduction of energy efficiency and reduced water flows would reduce summer energy generation capacity across the Southwest region. These projected reductions would increase risks of electricity shortages. 9 https://nca2018.globalchange.gov/chapter/25/ • Highlighted by McCabe et al. 2017, Udall and Overpeck 2017, and Woodhouse et al. 2016. 10 https://nca2018.globalchange.gov/chapter/25/ • Estimated by Udall and Overpeck 2017. 11 http://reportcard.statesatrisk.org/report-card/colorado/drought_grade • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 12 https://nca2018.globalchange.gov/chapter/25#fig-25-8 • Under a higher emissions scenario (SRES A2174), heat-induced reduction of water flows would reduce summer energy generation capacity across the Southwest region. 13 http://ecowest.org/tag/university-of-new-hampshire/ • Colorado has the highest employment of state winter tourism jobs and has the most visitors of any state for winter tourism. Both heat and drought can have an impact on this integral part of Colorado’s economy. 14 http://www.climatecentral.org/gallery/graphics/hotter-years-more-fires • Authors analyzed 45 years of U.S. Forest Service records of large wildfires (those fires burning more than 1,000 acres) from the western U.S. in the new report, “Western Wildfires: A Fiery Future.” 15 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 16 https://nca2018.globalchange.gov/chapter/25 • The increased projected fire frequency is based upon a higher emissions scenario (SRES A2). 17 https://nca2018.globalchange.gov/chapter/25/

• Demonstrated by Hohner et al. 2016 and Writer et al. 2014. 5. FLORIDA

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Temperatures in Florida Florida is expected to see Mosquito season in have increased by nearly nearly 8 times more heat Daytona Beach is now 2°F since 1970,1 and by wave days by 2050, from nearly a month longer than over 2.5°F during winter.2 around 10 to nearly 80 in 1980.6 Some cities in days a year – an increase southern Florida already Florida is already home to more than any other state.4 have suitable conditions HEAT 10 of the top 25 hottest year-round for adult cities in the U.S.; Miami is Also more than any other mosquitos that can spread the hottest city in the U.S.3 state, Florida is expected to dengue, chikungunya, and see 5 times more Zika viruses.7 dangerous heat days in 2050.5

Hurricanes in the Atlantic Florida is expected to see More than half a million have been stronger in the up to 4 feet of additional people and 400,000+ past couple of decades sea level rise from 2000 homes accounting for than during the levels by 2100.10 $200B+ in property value 1970s/1980s.8 are located within 4 feet of current sea level in 11 COASTAL Key West has had more Florida. than 6 times the amount of FLOODING coastal flood days in the Florida has 3.5 million past decade than in the people at risk for a 100- 1960s.9 year coastal flood;12 these floods may become 100 times more likely by 2050.13

Florida has experienced a By 2050, Florida’s inland More than 150 gallons of 20-30% increase in heavy flooding threat is projected sewage has spilled in St. downpours since 1950.14 to increase by 50%.15 Petersburg due to heavy rain events.16 INLAND More than 1.5 million FLOODING people in Florida are currently living in flood prone areas; this is more than in any other state.17

1 http://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 https://www.climatecentral.org/gallery/graphics/seasonal-warming-trends-across-the-us • Trends for meteorological seasons are calculated using monthly average temperature data between 1970 and 2017 (data from the NOAA NCEI). For clarity and the ability to compare different seasons, authors omitted the annual data points and displayed only the linear trends over time.

3 https://www.climatecentral.org/news/fastest-warming-cities-20535 • This analysis considered the top 200 largest metro areas in the U.S. and calculated their average annual temperature from 1981-2010. To determine which of those 200 cities have been warming the fastest, authors calculated how average annual temperatures have been changing since 1965. 4 http://assets.statesatrisk.org/summaries/Florida_report.pdf • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline (1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 5 http://assets.statesatrisk.org/summaries/Florida_report.pdf • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 6 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553 • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 7 https://nca2018.globalchange.gov/chapter/19/ • These climatic conditions specifically are suitable for adult mosquitoes of the species Aedes aegypti. 8 https://www.climatecentral.org/news/atlantic-hurricane-season-major-storms-20682 • The incidence of major hurricanes (Category 3 or higher) has essentially doubled across the Atlantic basin since 1970, potentially linked to rising sea surface temperatures there. 9 https://www.climatecentral.org/gallery/graphics/natural-human-caused-coastal-flood-days-in-the-us1 • Authors subtracted yearly estimates for human-caused global sea level rise based on Kopp et al. 2016, from hourly water level records at 27 tide gauges around the United States. They then compared how many days the water level exceeded the local threshold for nuisance flooding — with or without the subtractions. 10 https://riskfinder.climatecentral.org/api/reports/state/florida.us/state-report?lang=en • This analysis projects a main range of local sea level rise from 0.6-1.3 feet by 2050, and 1.7-4.7 feet by 2100, at Key West, using sea level in 2012 as the baseline. End-of-century projections at the seven other water level stations analyzed around the state range from about 3 inches lower (Apalachicola) to about 2 inches higher (Vaca Key). Projections align closely with the unified sea level rise projections of the Southeast Florida Regional Climate Change Compact (2011). 11 https://riskfinder.climatecentral.org/api/reports/state/florida.us/state-report?lang=en • 2120 square miles of land lie less than 3 feet above the high tide line in Florida. Some $145 billion in property value, and 300,000 homes, sit on that land. These figures jump to $544 billion and 1.4 million homes on 4660 square miles of land under 6 feet. 12 http://assets.statesatrisk.org/summaries/Florida_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 13 https://www.climatecentral.org/gallery/graphics/sea-level-rise-is-increasing-coastal-flood-risk • Source data comes from the Intermediate High NCA Projection and Climate Central. 14 https://www.climatecentral.org/news/heavy-rain-sewage-overflows-20718 • Data is retrieved from the Applied Climate Information System (rcc-acis.org). 15 https://www.climatecentral.org/gallery/maps/report-inland-flooding-to-increase-in-the-us • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico.

16 https://www.climatecentral.org/news/heavy-rain-sewage-overflows-20718 • Authors conducted a survey of news reports of rain-related overflows from January 2015 through August 2016. For each of these events, they confirmed how extreme the rain was, and in the case of several record-breaking rain events, further examined the volume of sewage that was reported. 17 http://assets.statesatrisk.org/summaries/Florida_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 6. IDAHO

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Idaho has warmed 2.6 °F By 2050, the typical Mosquito season in Boise on average since the number of heat wave days is currently about twice as 1970s.1 in Idaho is expected to long as it was in the triple3 and Boise is 1980s.6 Boise now experiences projected to experience more than twice as many Idaho has more than HEAT over 7 additional days above 100 °F per year in dangerous heat days.4 40,000 residents especially comparison to the 1970s.2 vulnerable to extreme Summers in Boise, heat.7 Meridian, and Nampa are projected to be 13 °F hotter by the end of the century.5 The severity of widespread By 2050, Idaho is projected Production of potatoes and drought in Idaho is to see a 110% increase in trout will be impacted by currently ranked in the top the threat of drought.9 drought, and Idaho is the 10 worst affected states in biggest producer of each the US.8 In the Northwest, years of product in the United DROUGHT abnormally low States.11 precipitation and extended drought conditions are expected to occur throughout the next century.10 Idaho now observes 21 By 2050, the number of 564,000 people in Idaho additional large wildfires high wildfire potential days (35% of the state’s per year and over 305,000 in Idaho is projected to population) live in the more acres burned per quadruple.13 wildland-urban interface, year compared to the highly vulnerable to WILDFIRES 1970s, the largest increase wildfire. But more of of any US state.12 Idaho’s wildfires occur in the remote forested land with the potential to impact the timber industry.14

1 https://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 3 http://assets.statesatrisk.org/summaries/Idaho_report.pdf 4 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 5 https://www.climatecentral.org/news/summer-temperatures-co2-emissions-1001-cities-16583 • Authors projected summer high temperatures for the end of this century for 1,001 cities, and then showed which city in the U.S. (or elsewhere in the world) is experiencing those temperatures today.

6 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553 • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 7 http://assets.statesatrisk.org/summaries/Idaho_report.pdf 8 http://assets.statesatrisk.org/summaries/Idaho_report.pdf 9 https://reportcard.statesatrisk.org/report-card/idaho/drought_grade 10 https://nca2018.globalchange.gov/chapter/24/ 11 https://agri.idaho.gov/main/ 12 http://assets.statesatrisk.org/summaries/Idaho_report.pdf 13 http://assets.statesatrisk.org/summaries/Idaho_report.pdf 14 http://assets.statesatrisk.org/summaries/Idaho_report.pdf 7. IOWA

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Winter temperatures in By midcentury, Iowa is Mosquito season in Iowa have warmed over 4 projected to experience Davenport is currently °F on average since the about 8 times as many almost a month longer than 1970s.1 dangerous heat days per in the 1980s.6 year.3 Summers in the Ohio Iowa has almost 70,000 Valley have warmed by as Summers in Des Moines people especially much as 2 °F over the are projected to be 11 °F vulnerable to extreme HEAT same time period.2 hotter by the end of the heat.7 century.4

The number of heat wave days in Iowa are projected to increase by 50 days per year by 2050.5

Iowa’s severity of By 2050, the severity of Rapid increases in air and widespread summer widespread summer water temperature and drought is currently below drought in Iowa is projected increasing drought risk will average compared to other to increase by 70%.9 likely accelerate the rate of DROUGHT states.8 species declines and extinctions in the Midwest.10

Heavy downpour events in By 2050, Iowa’s inland More than 150,000 people Iowa have increased by flooding threat is projected in Iowa are currently living 28% on average since to increase by about in flood-prone areas.15 1950.11 20%.13 INLAND FLOODING Heavy downpour events in A 100-year flood in the De Moines have increased Cedar River Basin is by 86% on average since projected to be 4 times as 1950.12 likely by the end of the century.14

1 https://www.climatecentral.org/gallery/graphics/seasonal-warming-trends-across-the-us • Trends for meteorological seasons are calculated using monthly average temperature data between 1970 and 2017 (data from the NOAA NCEI). For clarity and the ability to compare different seasons, authors omitted the annual data points and displayed only the linear trends over time. 2 https://www.climatecentral.org/gallery/maps/summer-temperature-trends • Summer is defined as the months of June, July, and August, analyzed over the period from 1970-2014. Source data comes from the NOAA/NCEI Climate at a Glance dataset. 3 http://assets.statesatrisk.org/summaries/Iowa_report.pdf • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 4 https://www.climatecentral.org/news/summer-temperatures-co2-emissions-1001-cities-16583

• Authors projected summer high temperatures for the end of this century for 1,001 cities, and then showed which city in the U.S. (or elsewhere in the world) is experiencing those temperatures today. 5 http://assets.statesatrisk.org/infographics/IA_infographic.pdf • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline (1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 6 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553 • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 7 http://assets.statesatrisk.org/summaries/Iowa_report.pdf • Especially vulnerable people are under 5 years old or 65 and older, living in poverty. 8 https://www.climatecentral.org/news/more-rain-less-snow-as-world-warms-20204 • This analysis of 65 years of winter precipitation data from more than 2,000 weather stations in 42 states, found a decrease in the percent of precipitation falling as snow in winter months for every region of the country. Winter months were defined as the snow season for each station, from the month with the first consistently significant snow, to the last. 9 http://assets.statesatrisk.org/summaries/Iowa_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 10 https://nca2018.globalchange.gov/chapter/21/ • Demonstrated by Perason et al. 2014 and Crausbay et al. 2017. 11 https://www.climatecentral.org/news/across-us-heaviest-downpours-on-the-rise-18989 • This analysis examines the heaviest downpours — the days where total precipitation exceeded the top 1 percent of all rain and snow days — at over 3,000 rain gauges distributed across the country over the period 1950-2014. 12 https://www.climatecentral.org/news/across-us-heaviest-downpours-on-the-rise-18989 • This analysis examines the heaviest downpours — the days where total precipitation exceeded the top 1 percent of all rain and snow days — at over 3,000 rain gauges distributed across the country over the period 1950-2014. 13 http://assets.statesatrisk.org/summaries/Iowa_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 14 https://nca2018.globalchange.gov/chapter/21/ • The 100-year flood of the 20th century in this region is projected to be a 25-year flood in the 21st century, with associated increased frequency of flooding of agricultural land (Anderson et al. 2015). 15 http://assets.statesatrisk.org/summaries/Iowa_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 8. MAINE

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Maine has warmed an Summers in Acadia Mosquito season in average of 2.6 °F since National Park are projected Portland has increased by 1970,1 while Maine winters to be 10 °F hotter by 2100,3 more than a month in have warmed over 4 °F and Portland is projected to length since the 1980s, the over the same time period.2 experience 7 times as 6th most of any US city.5 many dangerous heat days by 2050.4 Portland has experienced a HEAT 3 °F rise in dew point temperature since the 1980s. The additional moisture in the air increases risk of heatstroke and heat exhaustion.6

The Atlantic Coast By 2050, Maine’s coastal Maine has more than 7,000 experienced almost 3,000 flood threat is projected to people at risk of a 100-year coastal flood days in the increase by 85%, placing coastal flood.9 period from 2005-2014. an additional 6,000 people COASTAL in the 100-year coastal Maine currently has 100 This is almost 5 times as floodplain.8 square miles in the 100- FLOODING many coastal flood days as year coastal floodplain. By in the period from 1955- 2050, this is projected to 1964.7 increase to nearly 150 square miles.10

Maine has experienced a By 2050, Maine’s inland More than 135,000 people 61% increase in the flooding threat is projected – 10% of the state – are INLAND number of heavy to rank in the top 5 worst- living in flood prone areas, FLOODING downpours since 1950.11 affected states.12 the greatest percentage among 35 states assessed.13

1 https://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 https://www.climatecentral.org/gallery/graphics/seasonal-warming-trends-across-the-us • Trends for meteorological seasons are calculated using monthly average temperature data between 1970 and 2017 (data from the NOAA NCEI). For clarity and the ability to compare different seasons, authors omitted the annual data points and displayed only the linear trends over time. 3 https://www.climatecentral.org/news/national-parks-future-global-warming-20623 • Future temperatures for 47 National Parks were calculated based on the median of 29 spatially downscaled climate models (CMIP5) at 1/8 degree scale, then averaged within park boundaries. Temperatures for 2050 are based on the 20-year average of 2041-2060 and for 2100 are based on the period 2080-2099. Projected temperatures assume that greenhouse gas emissions continue at their current rate (RCP8.5). 4 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays

• “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 5 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553#dropdown • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 6 https://www.climatecentral.org/gallery/graphics/summers-getting-muggier-as-dewpoint-temp-rises • Dewpoint data was converted from vapor pressure. Vapor pressure data was obtained from the Daymet dataset at the Oak Ridge National Laboratory. 7 https://www.climatecentral.org/gallery/graphics/natural-human-caused-coastal-flood-days-in-the-us1 • Authors subtracted yearly estimates for human-caused global sea level rise based on Kopp et al. 2016, from hourly water level records at 27 tide gauges around the United States. They then compared how many days the water level exceeded the local threshold for nuisance flooding — with or without the subtractions. 8 http://assets.statesatrisk.org/summaries/Maine_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 9 http://assets.statesatrisk.org/summaries/Maine_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 10 http://assets.statesatrisk.org/summaries/Maine_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 11 https://www.climatecentral.org/news/across-us-heaviest-downpours-on-the-rise-18989 • This analysis examines the heaviest downpours — the days where total precipitation exceeded the top 1 percent of all rain and snow days — at over 3,000 rain gauges distributed across the country over the period 1950-2014. 12 http://assets.statesatrisk.org/summaries/Maine_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 13 http://assets.statesatrisk.org/summaries/Maine_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 9. MINNESOTA ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Voyageurs National Park Minneapolis is projected to Mosquito season in has warmed more than 2 experience more than 7 Minneapolis is currently °F over the past century.1 times more dangerous heat about a month longer than days by midcentury3 and in the 1980s, the 3rd Summers are muggier as the number of heat wave largest increase of any the dewpoint temperature days is projected to U.S. city.6 rises. In Duluth, the increase by more than five- dewpoint temperature has fold.4 Minneapolis has HEAT risen by over 2 °F since experienced a 4 °F 1980.2 Summers in St. Paul are increase in dew point projected to be 12 °F hotter temperature since the by the end of the century.5 1980s. The additional moisture in the air increases risk of heatstroke and heat exhaustion.7

Summer precipitation has By 2050, the severity of Rapid increases in air and slightly declined in widespread summer water temperature and Northeast Minnesota since drought in Minnesota is increasing drought risk will 1970.8 projected to nearly triple. likely accelerate the rate of This is the fourth greatest species declines and DROUGHT increase of any U.S. state extinctions in the and would make it one of Midwest.10 the five worst drought- affected states.9

In the Midwest, billion- Climate projections The average annual dollar floods have occurred suggest an increased risk damages from increased INLAND three times in the last 25 of inland flooding in the flooding risk in the Midwest years.11 Midwest under both high are projected to be more FLOODING and low emissions than $500 million by scenarios.12 midcentury.13

1 https://www.climatecentral.org/gallery/graphics/100-years-of-warming-at-the-national-parks • Source data from Hadley CRU Hi-Res Dataset. 2 https://www.climatecentral.org/gallery/graphics/summers-getting-muggier-as-dewpoint-temp-rises • Dewpoint data was converted from vapor pressure. Vapor pressure data was obtained from the Daymet dataset at the Oak Ridge National Laboratory. 3 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 4 http://assets.statesatrisk.org/summaries/Minnesota_report.pdf • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline (1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming.

5 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 6 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553#dropdown • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 7 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 8 https://www.climatecentral.org/gallery/maps/summer-precipitation-trends1 9 http://assets.statesatrisk.org/summaries/Minnesota_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 10 https://nca2018.globalchange.gov/chapter/21/ • Demonstrated by Perason et al. 2014 and Crausbay et al. 2017. 11 https://nca2018.globalchange.gov/chapter/21/ • Highlighted by the 2018 NOAA NCEI web page, “Billion-Dollar Weather and Climate Disasters.” 12 https://nca2018.globalchange.gov/chapter/21/ • The high and low emissions scenarios are represented by Representative Concentration Pathway Scenarios RCP8.5 and RCP4.5, respectively. 13 https://nca2018.globalchange.gov/chapter/21/ • As outlined by the 2017 EPA analysis, “Multi-model Framework for Quantitative Sectoral Impacts Analysis: A Technical Report for the Fourth National Climate Assessment.” 10. MISSOURI ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES In St. Louis, there is nearly The number of dangerous Missouri has more than one week more of days heat days (heat index 170,000 people 65 and above 95F each year than above 105F) a year in St. older, or under 5 years old, in 1970.1 Louis is expected to living below the poverty quadruple by 2050 – from line; these groups are 12 to 63.2 considered to be especially vulnerable to extreme HEAT St. Louis summers are heat.4 expected to be 11F hotter by 2100, which means Mosquito season in St. summers will be similar to Louis is now around one today’s summers at the month longer than it was in southern tip of Texas.3 the 1980s.5

The southeastern part of The severity of widespread Drought is a major concern Missouri has experienced a drought in Missouri is for farmers due to water declining trend in projected to increase by supply issues that affect precipitation since the nearly 70%.7 crops such as corn and hay DROUGHT 1970s.6 for cattle.

Pastures recovering from drought can become toxic for cattle.8 Forests are an integral part The number of days a year Over a million people in of Missouri culture, with high wildfire potential Missouri live within economics, pastimes, and in Missouri is projected to the wildland-urban WILDFIRE ecosystems.9 double from less than interface, where 10 to more than 20 days.10 vulnerability to wildfire is elevated.11 Billion-dollar floods in the By 2050, Missouri’s inland More than 200,000 people Midwest have occurred flooding threat is projected in Missouri are living in three times in the last to increase by around flood prone areas.15 quarter-century.12 40%.14 INLAND FLOODING Heavy downpours in Missouri are increasing – there are now 20 to 40% more of these events than in the 1950s.13

1 https://www.climatecentral.org/news/sizzling-summers-20515#daysabove 2 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays 3 https://www.climatecentral.org/news/summer-temperatures-co2-emissions-1001-cities-16583 4 http://assets.statesatrisk.org/summaries/Missouri_report.pdf 5 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553#dropdown

6 https://www.climatecentral.org/gallery/maps/summer-precipitation-trends1 7 http://assets.statesatrisk.org/summaries/Missouri_report.pdf 8 https://www.farmprogress.com/forage/pastures-recovering-after-drought-could-be-toxic-cattle 9 https://nca2018.globalchange.gov/chapter/21/ 10 http://assets.statesatrisk.org/summaries/Missouri_report.pdf 11 http://assets.statesatrisk.org/summaries/Missouri_report.pdf 12 https://nca2018.globalchange.gov/chapter/21/ 13 https://www.climatecentral.org/gallery/graphics/when-it-rains-it-pours 14 http://assets.statesatrisk.org/summaries/Missouri_report.pdf 15 http://assets.statesatrisk.org/summaries/Missouri_report.pdf 11. NEVADA ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES The state of Nevada has Heat wave days in Nevada Reno ranks 1st in U.S. observed 2.6°F warming are expected to quadruple cities with the largest since the 1970s.1 by 2050.3 increase in ‘disease danger days’ (risk of disease Reno is the fastest Las Vegas is expected to transmission by warming city in the U.S. experience nearly a month mosquitos), increasing by and Las Vegas is the 3rd.2 more of ‘dangerous’ heat 52 days since 1970.6 HEAT days by midcentury.4 Areas suitable for certain Summers in Great Basin crops are expected to shift National Park are expected by the end of the century to increase by 12°F by the due to increasing minimum end of the century.5 average temperatures.7

The Southwest U.S. is The severity of Nevada’s Las Vegas’s water supply already the most arid part summer drought is is threatened by depletion of the U.S., and research expected to increase by of surface water reservoirs. indicates that it is more than 30% by 2030.10 At current rates, Lake becoming even more dry.8 Mead levels could drop low DROUGHT There’s an 80% chance the enough by 2020 that it Over the past 30 years, Southwest could would cut off most of Las rainy patterns in the experience a megadrought Vegas’s water supply.12 Southwest are becoming lasting decades as the less frequent.9 climate warms.11

In the past 10 years, By midcentury, Nevada is More than 1.2 million Nevada has experienced expected to experience 20 people living in Nevada – twice the amount of fires additional high wildfire 46% of the state’s burning on U.S. Forest potential days compared to population – are at Service land compared to current rates.14 elevated risk of wildfire.16 the 1970s.13 WILDFIRES Without action to curb climate change, the Sierra Nevada may see triple the area burned yearly by 2100.15

1 http://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 http://www.climatecentral.org/news/fastest-warming-cities-20535 • This analysis considered the top 200 largest metro areas in the U.S. and calculated their average annual temperature from 1981-2010. To determine which of those 200 cities have been warming the fastest, authors calculated how average annual temperatures have been changing since 1965. 3 http://reportcard.statesatrisk.org/report-card/nevada/extreme_heat_grade • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline

(1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 4 http://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 5 http://www.climatecentral.org/news/national-parks-future-global-warming-20623 • Future temperatures for 47 National Parks were calculated based on the median of 29 spatially downscaled climate models (CMIP5) at 1/8 degree scale, then averaged within park boundaries. Temperatures for 2050 are based on the 20-year average of 2041-2060 and for 2100 are based on the period 2080-2099. Projected temperatures assume that greenhouse gas emissions continue at their current rate (RCP8.5). 6 https://www.climatecentral.org/news/us-faces-a-rise-in-mosquito-disease-danger-days-21903 • Temperature trends were calculated using average daily temperature data from the Applied Climate Information System (rcc-acis.org). Years with more than 30 days of missing data were excluded from the analysis. The temperature range of disease transmission (61-93F) as well as the range for peak transmission (79-84F) were chosen based on the findings in Mordecai et al. 2017. 7 https://nca2018.globalchange.gov/chapter/25/ • Under continued climate change, higher temperatures would shift plant hardiness zones northward and upslope. The U.S. Department of Agriculture plant hardiness zones indicate the cold temperature requirements of crops. Increases in temperature under the higher scenario (RCP8.5), would shift these zones northward and upslope, from the period 1976—2005 compared to projections for 2070—2099. 8 https://www.climatecentral.org/news/southwest-drier-climate-change-19990 • Authors apply a weather type (WT) analysis to reanalysis data from 1979–2014 that characterize typical weather conditions over the contiguous United States, enabling them to assign precipitation trends within 1980–2010 to changes in WT frequencies and changes in precipitation intensities. 9 https://www.climatecentral.org/news/southwest-drier-climate-change-19990 • Authors apply a weather type (WT) analysis to reanalysis data from 1979–2014 that characterize typical weather conditions over the contiguous United States, enabling them to assign precipitation trends within 1980–2010 to changes in WT frequencies and changes in precipitation intensities. 10 http://assets.statesatrisk.org/summaries/Nevada_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 11 https://www.climatecentral.org/news/southwest-drier-climate-change-19990 • Ault 2012 (“Assessing the Risk of Persistent Drought using Climate Model Simulations and Paleoclimate Data”) estimates the chances of a megadrought lasting 35 years or longer at up to 50 percent in the region. 12 https://www.nytimes.com/2014/06/18/us/arizona-cities-could-face-cutbacks-in-water-from-colorado-river- officials-say.html?_r=0 • If upstream states continue to be unable to make up the shortage, Lake Mead, whose surface is now about 1,085 feet above sea level, will drop to 1,000 feet by 2020. Under present conditions, that would cut off most of Las Vegas’s water supply. 13 http://reportcard.statesatrisk.org/report-card/nevada/wildfires_grade • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 14 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a

suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 15 https://nca2018.globalchange.gov/chapter/25/ • These increased burned area projections assume a higher emissions scenario (SRES A2). 16 http://reportcard.statesatrisk.org/report-card/nevada/wildfires_grade • Individuals living within the wildland-urban interface, where developed wild lands converge and intersperse, are at elevated risk for wildfire. 12. NEW MEXICO

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES New Mexico has warmed New Mexico is expected to There are currently 80,000 an average of 3°F since see twice as many people in New Mexico 1970,1 and the state’s dangerous heat days by especially vulnerable to summers are warming 2050,3 and more than 3 extreme heat.6 faster than any other state times as many heat wave in the U.S.2 days.4 Summer heat in Albuquerque is up to 22°F HEAT Summers in Carlsbad hotter than in nearby rural Caverns national Park are areas. This is the second projected to be 13°F hotter largest urban heat island in by year 2100, and to the country.7 experience 9 times as many days above 100°F per year.5

New Mexico’s current The severity of New Increased temperatures widespread summer Mexico’s summer drought have significantly altered drought severity is far is expected to increase by the water cycle in the above average and ranks more than 70% by 2050.10 Southwest. These changes in the top 5 in the country.8 are primarily attributed to DROUGHT There’s an 80% chance the climate change and Over the past 30 years, Southwest could exacerbate drought.12 rainy patterns in the experience a megadrought Southwest are becoming lasting decades as the less frequent.9 climate warms.11

Over the past five years, By midcentury, New More than 1.4 million New Mexico experienced Mexico is expecting to people living in New an average of 4 more large experience 25 additional Mexico – 70% of the state’s wildfires and 104,000 more high wildfire potential days population – are at WILDFIRES acres burning in large per year compared to elevated risk of wildfire. wildfires than in the current rates. This is tied This is the second largest 1970s.13 for the third-largest in the proportion among western country.14 states.15

1 https://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 3 http://assets.statesatrisk.org/summaries/NewMexico_report.pdf • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 4 http://assets.statesatrisk.org/summaries/NewMexico_report.pdf

• The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline (1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 5 https://www.climatecentral.org/news/national-parks-future-global-warming-20623 • Future temperatures for 47 National Parks were calculated based on the median of 29 spatially downscaled climate models (CMIP5) at 1/8 degree scale, then averaged within park boundaries. Temperatures for 2050 are based on the 20-year average of 2041-2060 and for 2100 are based on the period 2080-2099. Projected temperatures assume that greenhouse gas emissions continue at their current rate (RCP8.5). 6 http://assets.statesatrisk.org/summaries/NewMexico_report.pdf • Especially vulnerable people are under 5 years old or 65 and older, living in poverty. 7 https://www.climatecentral.org/news/urban-heat-islands-threaten-us-health-17919 • Temperature data is drawn from the Applied Climate Information Systems database (ACIS), which itself draws on data from NOAA/NCDC’s Global Historical Climatology Network (GHCN). For each of the 60 cities studied, a single urban station was identified as being closest to downtown and having a continuous temperature record for the period 1970-2013. In many cases, this was the city’s airport station. For each city, authors compared urban station data to rural temperatures in the surrounding climate. 8 http://assets.statesatrisk.org/summaries/NewMexico_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 9 https://www.climatecentral.org/news/southwest-drier-climate-change-19990 • Authors apply a weather type (WT) analysis to reanalysis data from 1979–2014 that characterize typical weather conditions over the contiguous United States, enabling them to assign precipitation trends within 1980–2010 to changes in WT frequencies and changes in precipitation intensities. 10 http://assets.statesatrisk.org/summaries/NewMexico_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 11 https://www.climatecentral.org/news/southwest-drier-climate-change-19990 • Ault 2012 (“Assessing the Risk of Persistent Drought using Climate Model Simulations and Paleoclimate Data”) estimates the chances of a megadrought lasting 35 years or longer at up to 50 percent in the region. 12 https://nca2018.globalchange.gov/chapter/25/ • Evidence of the altered water cycle is outlined in Fyfe et al. 2017, Mote et al. 2016, Mote et al. 2018, Pierce et al. 2008, Clow 2010, and Barnett et al. 2008. Pierce et al. 2008 and Barnett et al. 2008 also provide attribution analysis for climate change’s associated impact. 13 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 14 http://assets.statesatrisk.org/summaries/NewMexico_report.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 15 http://assets.statesatrisk.org/summaries/NewMexico_report.pdf

• Individuals living within the wildland-urban interface, where developed wild lands converge and intersperse, are at elevated risk for wildfire. 13. NEW YORK

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES New York is on average Buffalo is projected to Mosquito season in Albany 2.7 °F hotter than in year experience 15 times as is now about a month 1970.1 many heat danger days3 longer than it was in the and the typical number of 1980s.6 A study of New York City heat wave days in New estimated that in 2013 York is projected to Dew point temperatures in there were 133 excess increase five-fold by Albany have increased by HEAT deaths due to extreme midcentury.4 almost 4 °F since 1980. heat.2 More moisture in the air Summers in Albany and increases the risk of Buffalo are projected to be heatstroke and heat about 10 °F hotter by exhaustion.7 2100.5

The Battery and Kings By 2050, New York’s More than 430,000 people Point have each coastal flood threat is are at risk of a 100-year experienced 39 coastal projected to increase by coastal flood in New York, flood days between 2005- more than 50%, putting an the third greatest 2014; 79% attributed to additional 230,000 people vulnerable population 12 COASTAL human-caused sea level in the 100-year coastal among states in the U.S. rise.8 floodplain.10 FLOODING Should sea level rise reach Storm flood heights driven A 100-year flood in 10 feet, 754,000 people will by hurricanes in New York Montauk will be 20 times be affected in New York City have increased by more likely by midcentury City.13 more than 3.9 feet over the due to sea level rise.11 last thousand years.9 New York has experienced By 2050, New York’s inland More than 240,000 people a 30-40% increase in flooding threat is projected in New York are living in heavy downpours14 and to increase by 35%.16 flood prone areas.17 INLAND now observes more than 3 FLOODING times as many days with heavy precipitation per year compared to 1950.15

1 https://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 https://nca2018.globalchange.gov/chapter/18/ • Underlying study is Matte et al. 2016. 3 https://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 4 http://assets.statesatrisk.org/summaries/NewYork_report.pdf • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline

(1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 5 https://www.climatecentral.org/news/summer-temperatures-co2-emissions-1001-cities-16583 • Authors projected summer high temperatures for the end of this century for 1,001 cities, and then showed which city in the U.S. (or elsewhere in the world) is experiencing those temperatures today. 6 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553 • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 7 https://www.climatecentral.org/gallery/graphics/summers-getting-muggier-as-dewpoint-temp-rises • Dewpoint data was converted from vapor pressure. Vapor pressure data was obtained from the Daymet dataset at the Oak Ridge National Laboratory. 8 https://www.climatecentral.org/news/climate-change-increases-sunny-day-floods-20784 • This analysis is based on a broader February 2016 Climate Central analysis that looked at the human- caused sea level rise contribution to nuisance flooding over a 65-year period. That study focused on 27 tidal gauges with high quality hourly water level records dating back several decades. 9 https://nca2018.globalchange.gov/chapter/18/ • Demonstrated by Reed et al. 2015. 10 http://assets.statesatrisk.org/summaries/NewYork_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 11 https://www.climatecentral.org/gallery/graphics/sea-level-rise-is-increasing-coastal-flood-risk • Source data comes from the Intermediate High NCA Projection and Climate Central. 12 http://assets.statesatrisk.org/summaries/NewYork_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 13 https://www.climatecentral.org/gallery/graphics/storm-surge-and-sea-level-rise-cities-at-risk • Surging Seas maps, graphics and information are backed by scientifically peer-reviewed Climate Central research papers, select examples of which are provided at http://sealevel.climatecentral.org/research/papers. 14 https://www.climatecentral.org/news/heavy-rain-sewage-overflows-20718 • Data is retrieved from the Applied Climate Information System (rcc-acis.org). 15 https://www.climatecentral.org/gallery/graphics/heavy-precipitation-a-city-view • Authors analyzed rainfalls (or rainfall equivalents) of 1”+, 2”+, and 3”+ in a single calendar day since 1950. The data come from 207 airports across the continental U.S. where records have been reliable and continuous since at least 1950, showing very clearly that there’s been an upward trend in rainfalls of 1”+, 2”+, and 3”+ nationwide with respect to the average from 1950 to 2014. The bar charts presented show the number of calendar days grouped into five-year totals, which should help average out the year-to- year weather fluctuations. 16 http://assets.statesatrisk.org/summaries/NewYork_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 17 http://assets.statesatrisk.org/summaries/NewYork_report.pdf

• Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 14. NORTH CAROLINA ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Summers in North Carolina Summers in Great Smoky Mosquito season in are now 2°F hotter on Mountains National Park Durham and Raleigh is average.1 are expected to be 12°F now more than a month hotter by 2100.3 longer than in 1980.5 Raleigh now experiences almost 20 more days The number of dangerous Raleigh and Greenville above 95°F per year than heat days each year in have experienced a 3°F HEAT in 1970.2 North Carolina is projected increase in dew point to increase by almost 6 temperature since 1980 times by 2050.4 and the additional moisture in the air increases risk of heatstroke and heat exhaustion.6

Wilmington has 2,000 square miles of 120,000 people living in experienced 376 coastal North Carolina are North Carolina are flood days over the last currently at risk of a 100- currently at risk for a 100- decade, 82% of which are year coastal flood. This is year coastal flood. By attributed to human projected to increase to midcentury, this is 7 COASTAL activities. nearly 2,700 square miles expected to increase by by 2050.9 45,000 additional people.11 FLOODING In comparison, only 14 coastal flood days were By midcentury, a 100-year observed from 1955-1965.8 flood in the Outer Banks is projected to become 9 times more likely.10

The Southeast has By 2050, North Carolina’s More than 450,000 people observed a 27% increase inland flooding threat is in North Carolina are in the amount of rain falling projected to increase by currently living in flood during heavy downpours.12 40%.14 prone areas.15

INLAND Charlotte is among the top Intensifying extreme rainfall 20 cities that have events stress infrastructure FLOODING observed the strongest in the Southeast. Many increase in heavy transportation and storm downpours since 1950.13 water systems were not designed to withstand these events.16

1 https://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 https://www.climatecentral.org/news/sizzling-summers-20515#daysabove • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 3 https://www.climatecentral.org/news/national-parks-future-global-warming-20623

• Future temperatures for 47 National Parks were calculated based on the median of 29 spatially downscaled climate models (CMIP5) at 1/8 degree scale, then averaged within park boundaries. Temperatures for 2050 are based on the 20-year average of 2041-2060 and for 2100 are based on the period 2080-2099. Projected temperatures assume that greenhouse gas emissions continue at their current rate (RCP8.5). 4 http://assets.statesatrisk.org/summaries/NorthCarolina_report.pdf • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 5 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553 • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 6 https://www.climatecentral.org/gallery/graphics/summers-getting-muggier-as-dewpoint-temp-rises • Dewpoint data was converted from vapor pressure. Vapor pressure data was obtained from the Daymet dataset at the Oak Ridge National Laboratory. 7 https://www.climatecentral.org/news/climate-change-increases-sunny-day-floods-20784#dropdown • This analysis is based on a broader February 2016 Climate Central analysis that looked at the human- caused sea level rise contribution to nuisance flooding over a 65-year period. That study focused on 27 tidal gauges with high quality hourly water level records dating back several decades. 8 https://www.climatecentral.org/news/climate-change-increases-sunny-day-floods-20784#dropdown • This analysis is based on a broader February 2016 Climate Central analysis that looked at the human- caused sea level rise contribution to nuisance flooding over a 65-year period. That study focused on 27 tidal gauges with high quality hourly water level records dating back several decades. 9 http://assets.statesatrisk.org/summaries/NorthCarolina_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 10 https://www.climatecentral.org/gallery/graphics/sea-level-rise-is-increasing-coastal-flood-risk • Source data comes from the Intermediate High NCA Projection and Climate Central. 11 http://assets.statesatrisk.org/summaries/NorthCarolina_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 12 https://www.climatecentral.org/gallery/maps/extreme-precipitation-events-are-on-the-rise • Data retrieved from Kenneth Kunkel, Cooperative Institute for Climate and Satellites, North Carolina State University, and NOAA NCDC. 13 https://www.climatecentral.org/news/across-us-heaviest-downpours-on-the-rise-18989 • This analysis examines the heaviest downpours — the days where total precipitation exceeded the top 1 percent of all rain and snow days — at over 3,000 rain gauges distributed across the country over the period 1950-2014. 14 http://assets.statesatrisk.org/summaries/NorthCarolina_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 15 http://assets.statesatrisk.org/summaries/NorthCarolina_report.pdf

• Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 16 https://nca2018.globalchange.gov/chapter/18/ • By 2050, the Southeast is the region expected to have the most vulnerable bridges. Increasing precipitation and extreme weather events will likely impact roads, freight rail, passenger rail, and transit infrastructure. 15. PENNSYLVANIA

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Compared to 1970, By midcentury, the number Mosquito season in Pennsylvania is more than of extremely dangerous Pittsburg and Harrisburg is 2°F hotter on average1 and heat days observed in currently about a month Pittsburg experiences over Pennsylvania is projected longer than in the 1980s.6 5 more days above 90°F to triple and the number of per year.2 heat wave days to increase Harrisburg has by five-fold.4 experienced an almost 4°F HEAT Erie is the 15th fastest increase in dew point warming city in the U.S. Summers in Harrisburg are temperature since the and Philadelphia is the expected to be 11°F hotter 1980s and the additional 17th.3 by the end of the century.5 moisture in the air increases risk of heatstroke and heat exhaustion.7

Philadelphia has By 2050, Pennsylvania’s Although Pennsylvania is experienced 304 coastal coastal flood risk is not generally considered as flood days since 1950, 53% expected to almost double, a coastal state, areas of which were human- putting an additional 6,000 bordering the tidal waters 8 COASTAL caused. people at risk of a 100-year of the Delaware Bay pose flood.10 risk for coastal flooding.11 FLOODING This is 6 times as many coastal flood days Pennsylvania has about experienced by the city 7,000 people at risk of a compared to 1955-1964.9 100-year coastal flood.12

On average, Philadelphia By 2050, Pennsylvania’s More than 430,000 people has experienced a 360% coastal flood threat may in Pennsylvania are living increase in heavy increase by roughly 40%, in flood prone areas.15 downpours since 1950, the one of the top 10 greatest 14 INLAND third most of any U.S. in the U.S. During Hurricane Sandy, city.13 Pennsylvania experienced FLOODING over 56 million gallons of sewage overflow associated with the storm surge.16

1 https://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 https://www.climatecentral.org/news/sizzling-summers-20515#daysabove • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 3 https://www.climatecentral.org/news/fastest-warming-cities-20535 • This analysis considered the top 200 largest metro areas in the U.S. and calculated their average annual temperature from 1981-2010. To determine which of those 200 cities have been warming the fastest, authors calculated how average annual temperatures have been changing since 1965.

4 http://assets.statesatrisk.org/summaries/Pennsylvania_report.pdf • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 5 https://www.climatecentral.org/news/summer-temperatures-co2-emissions-1001-cities-16583 • Authors projected summer high temperatures for the end of this century for 1,001 cities, and then showed which city in the U.S. (or elsewhere in the world) is experiencing those temperatures today. 6 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553 • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 7 https://www.climatecentral.org/gallery/graphics/summers-getting-muggier-as-dewpoint-temp-rises • Dewpoint data was converted from vapor pressure. Vapor pressure data was obtained from the Daymet dataset at the Oak Ridge National Laboratory. 8 https://www.climatecentral.org/gallery/graphics/natural-human-caused-coastal-flood-days-in-the-us1 • Authors subtracted yearly estimates for human-caused global sea level rise based on Kopp et al. 2016, from hourly water level records at 27 tide gauges around the United States. They then compared how many days the water level exceeded the local threshold for nuisance flooding — with or without the subtractions. 9 https://www.climatecentral.org/gallery/graphics/natural-human-caused-coastal-flood-days-in-the-us1 • Authors subtracted yearly estimates for human-caused global sea level rise based on Kopp et al. 2016, from hourly water level records at 27 tide gauges around the United States. They then compared how many days the water level exceeded the local threshold for nuisance flooding — with or without the subtractions. 10 http://assets.statesatrisk.org/summaries/Pennsylvania_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 11 http://assets.statesatrisk.org/summaries/Pennsylvania_report.pdf 12 http://assets.statesatrisk.org/summaries/Pennsylvania_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 13 https://www.climatecentral.org/news/across-us-heaviest-downpours-on-the-rise-18989 • This analysis examines the heaviest downpours — the days where total precipitation exceeded the top 1 percent of all rain and snow days — at over 3,000 rain gauges distributed across the country over the period 1950-2014. 14 http://assets.statesatrisk.org/summaries/Pennsylvania_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 15 http://assets.statesatrisk.org/summaries/Pennsylvania_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al.

(2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 16 https://www.climatecentral.org/news/11-billion-gallons-of-sewage-overflow-from-hurricane-sandy-15924 • Data for this analysis is provided by state agencies and individual plant operators. See full report, Sewage Overflows from Hurricane Sandy (here), for more detail.

16. SOUTH CAROLINA

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES The number of nights South Carolina is projected Mosquito season in South above 75°F in the to observe four times as Carolina is now over a Southeast U.S. have many heat wave days per month longer than it was in doubled since the 1980s.1 year by midcentury.3 the 1980s.5

HEAT Some cities, such as Charleston is expected to Agriculture is impacted by Columbia, SC, are experience 74 more a lack of nighttime cooling.6 experiencing 2 more weeks dangerous heat days by per year of days above midcentury.4 95°F.2

Hurricanes in the Atlantic Sea level rise is projected South Carolina has nearly have been stronger in the to increase up to 7 feet in 230,000 residents at risk of past couple of decades Charleston by the end of a 100-year flood.11 than during the 1970s/80s.7 the century.9 By 2050, South Carolina’s COASTAL The number of coastal By midcentury, a 100-year coastal flood threat is FLOODING flood days in Charleston flood in Charleston may projected to increase by has more than quadrupled become 9 times more 25%, putting an additional since the 1950s – 80% likely.10 55,000 people in the 100- have been attributed to year coastal floodplain.12 climate change.8

Heavy downpours have South Carolina’s inland Over 200,000 people in increased by 27% in the flooding threat is projected South Carolina live in flood- southeastern U.S. since to increase by 30% by prone areas.18 the 1950s.13 midcentury.16 Record flooding in South INLAND Charleston experienced all- Flood events in Charleston Carolina due to extreme FLOODING time record high tide flood have been increasing, and rainfall events has already occurrences in 2015 and by 2045 the city is cost billions of dollars and 2016.14 15 projected to face nearly dozens of lives.19 These 180 tidal floods per year in events are expected to comparison to 11 in 2014.17 intensify.20

1 https://nca2018.globalchange.gov/chapter/19#fig-19-1 • During the 2010s, the number of nights with minimum temperatures greater than 75°F was nearly double the long-term average for 1901–1960, while the length of the freeze-free season was nearly 1.5 weeks greater than any other period in the historical record. 2 http://www.climatecentral.org/news/sizzling-summers-20515#daysabove • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 3 http://reportcard.statesatrisk.org/report-card/south-carolina/extreme_heat_grade • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline

(1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 4 http://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 5 http://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553 • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 6 https://nca2018.globalchange.gov/chapter/19/ • Projected temperature increases pose challenges for crop production dependent on periods of lower temperatures to reach full productivity. 7 https://www.climatecentral.org/news/atlantic-hurricane-season-major-storms-20682 • The incidence of major hurricanes (Category 3 or higher) has essentially doubled across the Atlantic basin since 1970, potentially linked to rising sea surface temperatures there. 8 http://www.climatecentral.org/news/climate-change-increases-sunny-day-floods-20784 • This analysis is based on a broader February 2016 Climate Central analysis that looked at the human- caused sea level rise contribution to nuisance flooding over a 65-year period. That study focused on 27 tidal gauges with high quality hourly water level records dating back several decades. 9 https://nca2018.globalchange.gov/chapter/19#fig-19-10 • Maximum sea level rise based on the NOAA “High” sea level rise scenario. 10 http://www.climatecentral.org/gallery/graphics/sea-level-rise-is-increasing-coastal-flood-risk • Source data comes from the Intermediate High NCA Projection and Climate Central. 11 http://assets.statesatrisk.org/summaries/SouthCarolina_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 12 http://assets.statesatrisk.org/summaries/SouthCarolina_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 13 http://www.climatecentral.org/gallery/maps/extreme-precipitation-events-are-on-the-rise • Data retrieved from Kenneth Kunkel, Cooperative Institute for Climate and Satellites, North Carolina State University, and NOAA NCDC. 14https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_fin al.pdf • In order to bound the set of GMSL rise scenarios for year 2100, authors assessed the most up-to-date scientific literature on scientifically supported upper-end GMSL projections, including recent observational and modeling literature related to the potential for rapid ice melt in Greenland and Antarctica. The projections and results presented in several peer-reviewed publications provide evidence to support a physically plausible GMSL rise in the range of 2.0 meters (m) to 2.7 m, and recent results regarding Antarctic icesheet instability indicate that such outcomes may be more likely than previously thought. 15 http://www.ncdc.noaa.gov/monitoring-content/sotc/national/2016/may/sweet-marra-nuisance-flooding- 2015.pdf

• High tide flooding, measured locally by National Oceanic and Atmospheric Administration (NOAA) tide gauges, is described as “nuisance”, “sunny-day” and “recurrent”. Such minor flooding is increasingly common with little or no storm effects (Sweet et al., 2014). 16 http://assets.statesatrisk.org/summaries/SouthCarolina_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 17 https://nca2018.globalchange.gov/chapter/19/ • Tidal floods are defined as flooding in coastal areas at high tide. Estimates of projected increase drawn from the City of Charleston’s 2015 Sea Level Rise Strategy report. 18 http://assets.statesatrisk.org/summaries/SouthCarolina_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 19 https://nca2018.globalchange.gov/chapter/19#table-19-1 • Values are Consumer Price Index adjusted and are in 2017 dollars. Data source is NOAA NCEI 2017. 20 https://nca2018.globalchange.gov/chapter/19#case-19_3 • Under future climate scenarios, the combination of extreme precipitation and higher tides due to local sea level rise will likely cause more frequent events of this intensity and magnitude (CISA 2016). 17. TEXAS

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Austin now observes By 2050, Texas is Mosquito season in almost 40 more days projected to experience Lubbock is about 18 days above 100 °F than in almost twice as many longer than it was in the 19701, and Big Bend dangerous or extremely 1980s.6 National Park has warmed dangerous heat days per almost 3 °F since the year.4 Texas has 840,000 people HEAT 1900s.2 especially vulnerable to Summer temperatures in extreme heat.7 El Paso is the 9th fastest Big Bend National Park warming city in the may increase by 13 °F by country.3 2100.5

The Southern Great Plains By 2050, the severity of The severity of widespread region is prone to periods widespread summer summer drought in Texas of drought punctuated by drought is projected to ranks first among US heavy rainfall events, with almost double in Texas.9 states.10 evidence that these events DROUGHT are occurring more The Texas State Water frequently.8 Plan predicts that a growing population will yield a 17% increase in water demand by 2050.11

Periods of abundant By 2050, the average Nearly 18 million people in precipitation followed by number of days with high Texas (over 70% of the drought and high wildfire potential in Texas is state population) are at temperatures are linked to projected to double (the elevated vulnerability to increased wildfire activity in greatest increase of wildfire wildfire.15 WILDFIRES Texas.12 threat in any US state)13 and Texas will be the worst The Bastrop Fire, which wildfire-affected state in the took place during the U.S.14 drought of 2011, destroyed over 1,500 homes.16

Port Isabel has By 2050, Texas coastal 192,000 people in Texas experienced 121 coastal flooding threat is projected are currently at risk of a flood days since 2005, 85% to increase by about 60%, 100-year coastal flood.21 of which were human with an additional 115,000 17 COASTAL caused. people in the 100-year If sea level were to rise by coastal floodplain. 19 10 feet, 110,000 people FLOODING Along the Texas coastline, living in Galveston would sea level has risen 5-17 By 2050, a 100-year flood be affected.22 inches over the last 100 at Corpus Christi will be 9 years.18 times more likely.20

1 https://www.climatecentral.org/news/sizzling-summers-20515#daysabove

• “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 2 https://www.climatecentral.org/gallery/graphics/100-years-of-warming-at-the-national-parks • Source data from Hadley CRU Hi-Res Dataset. 3 https://www.climatecentral.org/news/fastest-warming-cities-20535 • This analysis considered the top 200 largest metro areas in the U.S. and calculated their average annual temperature from 1981-2010. To determine which of those 200 cities have been warming the fastest, authors calculated how average annual temperatures have been changing since 1965. 4 http://assets.statesatrisk.org/summaries/Texas_report.pdf • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 5 https://www.climatecentral.org/news/national-parks-future-global-warming-20623 • Future temperatures for 47 National Parks were calculated based on the median of 29 spatially downscaled climate models (CMIP5) at 1/8 degree scale, then averaged within park boundaries. Temperatures for 2050 are based on the 20-year average of 2041-2060 and for 2100 are based on the period 2080-2099. Projected temperatures assume that greenhouse gas emissions continue at their current rate (RCP8.5). 6 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553 • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 7 http://assets.statesatrisk.org/summaries/Texas_report.pdf • Especially vulnerable people are under 5 years old or 65 and older, living in poverty. 8 https://nca2018.globalchange.gov/chapter/23/ • Demonstrated by Christian et al. 2015. 9 http://assets.statesatrisk.org/summaries/Texas_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 10 http://assets.statesatrisk.org/summaries/Texas_report.pdf • Severity of widespread summer drought is defined as the sum of soil moisture deficit (standard score) in the summer months for model grid cells where the standard score is less than -1, when at least 30% of grid cells in a state meet this criterion. 11 https://nca2018.globalchange.gov/chapter/23/ • The Texas State Water Plan was produced by the Texas Water Development Board in 2017 and can be found here: http://www.twdb.texas.gov/waterplanning/swp/2017/doc/SWP17-Water-for-Texas.pdf. 12 https://nca2018.globalchange.gov/chapter/23/ • Demonstrated by Scasta et al. 2016. 13 http://assets.statesatrisk.org/summaries/Texas_report.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 14 http://assets.statesatrisk.org/summaries/Texas_report.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 15 http://assets.statesatrisk.org/summaries/Texas_report.pdf

• Individuals living within the wildland-urban interface, where developed wild lands converge and intersperse, are at elevated risk for wildfire. 16 https://nca2018.globalchange.gov/chapter/23/ • Texas experienced several major wildfire outbreaks during the drought of 2011, including the Bastrop Fire that destroyed more than 1,500 homes. 17 https://www.climatecentral.org/news/climate-change-increases-sunny-day-floods-20784#dropdown • This analysis is based on a broader February 2016 Climate Central analysis that looked at the human- caused sea level rise contribution to nuisance flooding over a 65-year period. That study focused on 27 tidal gauges with high quality hourly water level records dating back several decades. 18 https://nca2018.globalchange.gov/chapter/23/ • Rates of sea level rise depend upon local topography and subsidence (sinking of land). Supporting evidence from Runkle et al. 2017. 19 http://assets.statesatrisk.org/summaries/Texas_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 20 https://www.climatecentral.org/gallery/graphics/sea-level-rise-is-increasing-coastal-flood-risk • Source data comes from the Intermediate High NCA Projection and Climate Central. 21 http://assets.statesatrisk.org/summaries/Texas_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 22 https://www.climatecentral.org/gallery/graphics/storm-surge-and-sea-level-rise-cities-at-risk • Surging Seas maps, graphics and information are backed by scientifically peer-reviewed Climate Central research papers, select examples of which are provided at http://sealevel.climatecentral.org/research/papers. 18. UTAH

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Average temperatures in Salt Lake City is expected By 2050, some cities in Utah during spring and fall to experience twice as Utah could see up to a have warmed by over 3°F many dangerous heat days 30% reduction in electricity since 1970.1 by midcentury,2 and generation capacity during summers that are 11°F summer.5 hotter by 2100.3 Areas suitable for specific HEAT By 2100, summers in Zion crops are expected to shift national Park will feel like by the end of the century today’s summers in Lower due to increasing minimum Valley, Texas.4 average temperatures that are required for certain crops.6

The Southwest U.S. is Summer drought in Utah is Past drought conditions in already the most arid part projected to increase in Utah have impacted a of the U.S., and research severity by about 225% by majority of ranch indicates that it is 2050.9 operations in the state, becoming even more dry.7 including major reductions DROUGHT in water supply, forage, Over the past 30 years, and cattle productivity.10 rainy patterns in the Southwest are becoming less frequent.8

Utah now sees about 20 By 2050, Utah is projected Over 1.3 million people times more acres burned to observe 23 additional living in Utah – 45% of the by large wildfires annually high wildfire potential days state’s population – are in comparison to the 1970s per year.12 living in the wildland-urban WILDFIRES and six times more large interface and are highly wildfires burning each year vulnerable to wildfires.13 over the past ten years on US Forest Service land.11

1 https://www.climatecentral.org/gallery/graphics/seasonal-warming-trends-across-the-us • Trends for meteorological seasons are calculated using monthly average temperature data between 1970 and 2017 (data from the NOAA NCEI). For clarity and the ability to compare different seasons, authors omitted the annual data points and displayed only the linear trends over time. 2 http://www.climatecentral.org/news/sizzling-summers-20515#dangerdays • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 3 http://www.climatecentral.org/news/summer-temperatures-co2-emissions-1001-cities-16583 • Authors projected summer high temperatures for the end of this century for 1,001 cities, and then showed which city in the U.S. (or elsewhere in the world) is experiencing those temperatures today. 4 https://www.climatecentral.org/news/national-parks-future-global-warming-20623

• Future temperatures for 47 National Parks were calculated based on the median of 29 spatially downscaled climate models (CMIP5) at 1/8 degree scale, then averaged within park boundaries. Temperatures for 2050 are based on the 20-year average of 2041-2060 and for 2100 are based on the period 2080-2099. Projected temperatures assume that greenhouse gas emissions continue at their current rate (RCP8.5). 5 https://nca2018.globalchange.gov/chapter/25/ • Under a higher emissions scenario (SRES A2), heat-induced reduction of energy efficiency and reduced water flows would reduce summer energy generation capacity across the Southwest region. These projected reductions would increase risks of electricity shortages. 6 https://nca2018.globalchange.gov/chapter/25/ • Under continued climate change, higher temperatures would shift plant hardiness zones northward and upslope. The U.S. Department of Agriculture plant hardiness zones indicate the cold temperature requirements of crops. Increases in temperature under the higher scenario (RCP8.5), would shift these zones northward and upslope, from the period 1976—2005 compared to projections for 2070—2099. 7 https://www.climatecentral.org/news/southwest-drier-climate-change-19990 • Authors apply a weather type (WT) analysis to reanalysis data from 1979–2014 that characterize typical weather conditions over the contiguous United States, enabling them to assign precipitation trends within 1980–2010 to changes in WT frequencies and changes in precipitation intensities. 8 https://www.climatecentral.org/news/southwest-drier-climate-change-19990 • Authors apply a weather type (WT) analysis to reanalysis data from 1979–2014 that characterize typical weather conditions over the contiguous United States, enabling them to assign precipitation trends within 1980–2010 to changes in WT frequencies and changes in precipitation intensities. 9 http://reportcard.statesatrisk.org/report-card/utah/drought_grade • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 10 https://nca2018.globalchange.gov/chapter/25/ • In response to drought (1999–2004), 75% of Utah ranch operations reported major reductions in water supply, forage, and cattle productivity. Only 14% felt they were adequately prepared for the drought, which may be reflected in the high use of federal relief programs (Coppock 2011). 11 http://www.climatecentral.org/gallery/graphics/hotter-years-more-fires • Authors analyzed 45 years of U.S. Forest Service records of large wildfires (those fires burning more than 1,000 acres) from the western U.S. in the new report, “Western Wildfires: A Fiery Future.” 12 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 13 http://assets.climatecentral.org/pdfs/westernwildfires2016vfinal.pdf • Trends for wildfires in the 11 western states of the contiguous U.S. are calculated on large wildfires (those larger than 1,000 acres) occurring on U.S. Forest Service land between 1970-2015. These wildfires represent a significant percent of the total area burned each year in western wildfires, and thus they are a suitable representative of overall wildfire trends. Trends for Alaskan fires are based on large wildfires burning on both federal and state land across Alaska between 1950-2015. 19. VIRGINIA

ALREADY OBSERVED ANTICIPATED FUTURE RISKS TO SOCIETY CHANGES CHANGES Annual temperatures in The number of “dangerous” Mosquito season in Virginia have increased by or “extremely dangerous” Richmond is currently a 2°F since the 1970s,1 and heat days in Virginia is month longer than in the over 3°F in the wintertime.2 expected to more than 1980s.6 quadruple by 2050, Bristol, VA now currently averaging less Norfolk has experienced a than 10 per year.4 3 F increase in dew point HEAT experiences more than two ° weeks of additional temperature since the extreme heat days By 2050, the number of 1980s and the additional compared to the 1970s.3 heat wave days in Virginia moisture in the air is expected to increase by increases risk of heatstroke 6 times, from 10 to nearly and heat exhaustion.7 60 days per year.5

Hurricanes in the Atlantic By 2050, Virginia’s coastal During Hurricane Sandy, have been stronger in the flood threat may increase 18.3 million gallons of past couple of decades by 75% putting an sewage was spilled in than during the 1970s/80s.8 additional 140,000 people Suffolk due to equipment in the 100-year floodplain.10 failure. As Atlantic COASTAL Sea level rise in Norfolk hurricane season becomes has increased the chance Sea level rise by 2050 may more intense, the threat of FLOODING of exceeding flood increase coastal flooding similar spills increases.13 advisory/warning events by five times at the thresholds by 4 times Chesapeake Bay Bridge11 compared to the 1960s.9 and make a 100-year flood 25 times more likely.12

On average, Virginia has By 2050, Virginia’s inland 265,000 people in Virginia experienced a 20-30% flooding threat is projected are currently living in flood increase in heavy to increase by more than prone areas.17 downpours since 1950.14 20%.15 Intensifying extreme rainfall INLAND Without climate action, we events is stressing already expect double the number deteriorating infrastructure FLOODING of heavy rainfall events and in the Southeast. Many a 20% increase in the transportation and storm amount of rain falling water systems were not during heavy downpours in designed to withstand the Southeast by 2100.16 these events.18

1 https://www.climatecentral.org/news/us-warming-trend-earth-day-20257 • Since the 1970s, the contiguous 48 states have been warming at a rate of 0.45°F per decade. This analysis draws on temperature data from the national Climatic Data Center’s Climate at a Glance database. 2 https://www.climatecentral.org/gallery/graphics/seasonal-warming-trends-across-the-us

• Trends for meteorological seasons are calculated using monthly average temperature data between 1970 and 2017 (data from the NOAA NCEI). For clarity and the ability to compare different seasons, authors omitted the annual data points and displayed only the linear trends over time. 3 https://www.climatecentral.org/news/sizzling-summers-20515#daysabove • The projections draw on 29 global climate models that have been downscaled across the continental U.S. to represent local climate conditions. 4 http://assets.statesatrisk.org/summaries/Virginia_report.pdf • “Dangerous” and “extremely dangerous” heat days are classified by the National Weather Service Heat Index, taking into account both temperature and relative humidity. 5 http://assets.statesatrisk.org/summaries/Virginia_report.pdf • The annual number of heatwave days is calculated as the average number of days each year on which the daily maximum temperature exceeds the 95th percentile of daily maximum temperature in the baseline (1991-2010) period for at least three consecutive days. While days above this temperature are not all potentially harmful to human health, an increase in hot days is an indicator of general warming. 6 https://www.climatecentral.org/news/more-mosquito-days-increasing-zika-risk-in-us-20553#dropdown • The analysis of mosquito season length is based on the ideal temperature and humidity conditions for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus. These mosquitoes have high mortality rates at temperatures outside the range of 50-95°F or at relative humidity below 42 percent. 7 https://www.climatecentral.org/gallery/graphics/summers-getting-muggier-as-dewpoint-temp-rises • Dewpoint data was converted from vapor pressure. Vapor pressure data was obtained from the Daymet dataset at the Oak Ridge National Laboratory. 8 https://www.climatecentral.org/news/atlantic-hurricane-season-major-storms-20682 • The incidence of major hurricanes (Category 3 or higher) has essentially doubled across the Atlantic basin since 1970, potentially linked to rising sea surface temperatures there. 9 https://nca2018.globalchange.gov/chapter/19#fig-19-8 • This is compared to the National Weather Service high tide flooding threshold. 10 http://assets.statesatrisk.org/summaries/Virginia_report.pdf • The sea level rise and coastal flood analysis aimed to delineate zones with 1% annual flood risk (100-year coastal floodplains), given baseline and projected sea levels in the years 2000 and 2050, and to tabulate the current population residing within them. Median sea level rise (SLR) projections from Kopp et al. (2014) are for 2050 under RCP 8.5 at 69 tide gauges along the U.S. coast. The projections take vertical land motion into account. 11 https://www.climatecentral.org/gallery/graphics/climate-change-increasing-frequency-of-coastal-flooding • Observed water levels were used to count present and past floods, which were driven by tides along with storm surges. Future hourly water levels are based on detailed tidal projections and sea level rise projections. 12 https://www.climatecentral.org/gallery/graphics/sea-level-rise-is-increasing-coastal-flood-risk • Source data comes from the Intermediate High NCA Projection and Climate Central. 13 https://www.climatecentral.org/news/11-billion-gallons-of-sewage-overflow-from-hurricane-sandy-15924 • Data for this analysis is provided by state agencies and individual plant operators. See full report, Sewage Overflows from Hurricane Sandy (here), for more detail. 14 https://www.climatecentral.org/news/heavy-rain-sewage-overflows-20718 • Authors conducted a survey of news reports of rain-related overflows from January 2015 through August 2016. For each of these events, they confirmed how extreme the rain was, and in the case of several record-breaking rain events, further examined the volume of sewage that was reported. 15 https://www.climatecentral.org/gallery/maps/report-inland-flooding-to-increase-in-the-us • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 16 https://nca2018.globalchange.gov/chapter/19/

• This assumes a high emissions scenario (RCP8.5). Estimates from Easterling et al. 2017 and Allan and Soden 2008. 17 http://assets.statesatrisk.org/summaries/Virginia_report.pdf • Climate threat analysis was performed for outputs based on 29 GCMs available in the archive under the RCP 8.5 emissions scenario. These climate and hydrology projections have a spatial resolution of ⅛° (about 140 square kilometers per grid cell), and cover the conterminous United States and portions of Canada and Mexico. 18 https://nca2018.globalchange.gov/chapter/19/ • By 2050, the Southeast is the region expected to have the most vulnerable bridges. Increasing precipitation and extreme weather events will likely impact roads, freight rail, passenger rail, and transit infrastructure.